This invention relates to plastic, multi-part pulleys or sheaves that are provided with special, wear-resistant or friction surfaces intended to handle wire and like strand material, and more particularly to sheaves of this type which can be produced inexpensively and yet are of exceptionally high quality.
In my copending application above referred to I provide an improved sheave that is lagged with rubber or rubber-like material and comprises two disc-like members disposed broadside to each other and secured together to form an annular V-groove for receiving and guiding wire or like material. In the V-groove a rubber wear strip is held captive, and the hub portions of the disc-like members enclose a ball-bearing assemblage by which a low-friction bearing is had on the shaft or spindle. The rubber wear strip is cut from a length of extruded strip stock, and the ends are butted, forming a joint at one spot on the periphery of the sheave.
When a number of such sheaves are disposed in tandem on a common shaft and in close juxtaposition, the overall axial length of the assemblage can sometimes be in excess of the available space that is alloted, due to the width of the peripheral V-groove rim portions and also the width of the hub portions which mount the anti-friction bearing. It is not possible to arrange for a nesting of one sheave with an adjoining sheave to save or reduce the space on the spindle, and a certain amount of spacing is always necessary to prevent touching or rubbing of the sheaves.
The cutting of the rubber lagging strip required a careful, somewhat precise operation even with the employment of suitable sizing jigs or fixtures, and slight variations in the length would show up in the finished product and impair the appearance even though performance was not adversely affected.
Other prior sheaves for handling wire and like strands were not, to my knowledge, provided with rubber wear strips in the bottom portions of the V-grooves and did not have the wear-resistant advantages which come from the use of rubber or similar resilient substances arranged to be engaged by the strand material. Nor did these prior sheaves l end themselves to quick and easy replacement of the lagging substance in many instances, particularly where they were located in inaccessible spots.
The construction of prior sheaves involved tooling and assembly operations which brought up the fabricating cost unnecessarily, especially where a certain amount of labor was involved. In present-day products, labor-intensive components or assemblages are diligently avoided, wherever possible.